The present invention relates to a tunnel oven for making thermoshrinking material films packages.
The invention also relates to a packaging method for providing packages, the method being carried out in the inventive tunnel oven.
More specifically, the field of the invention is that of the tunnel ovens used for making thermoshrinking material film packages, for example for packaging bottles, cans and the like.
Prior systems for packaging articles in general, such as bottles, cans and so on, in thermoshrinking plastic material films, provide to use heated tunnel ovens, inside which the packages as preliminarily enveloped by the mentioned thermoshrinking film are conveyed.
The oven tunnel is heated by hot air jets, oriented against the articles to be packaged.
The size of the tunnel oven is so selected as to be compatible to the size of the articles to be packaged, to provide an efficient heating and thermo-shrinking process.
The above mentioned prior solutions are however affected by several drawbacks.
At first, the thermoshrinking plastic material films have usually an uneven thickness, which is conventionally modified by the application of decorations or advertisement patterns, which are randomly printed on the film surfaces.
Thus, the aspect of the obtained packages is frequently altered, thereby reflecting an unproper packaging process.
Furthermore, the requirement of designing the oven tunnels with a size related to that of the articles to be packaged represents a great limitation preventing the same oven from being used for articles of different size, i.e. having a size different from that for which the tunnel oven has been constructed.
A further drawback of the tunnel ovens of the prior art is that the film material enveloping the packaged articles tend to adhere to the chain conveying means of the oven, thereby hindering a proper hot air flow, and leaving undesired marks on the bottoms of the packaged articles, and, moreover, undesirably depositing plastic material debris on the oven conveying chains.
Accordingly, the aim of the present invention is to improve prior tunnel ovens, for making packages devoid of surface unevennesses to be used for a broad range of the article to be packaged size.
The above aim, as well as yet other objects, are achieved by tunnel oven and packaging method as respectively defined by claims 1 and 23.
Preferred embodiments of the tunnel oven and packaging method according to the present invention are defined by the subclaims.
With respect to the prior art, the tunnel oven and packaging method according to the present invention provide the advantage of providing thermoshrinking material packages devoid of surface unevennesses, and of even aspect, owing to the use of controlling means for controlling the air flows.
The invention provides moreover that it allows to process, in the same tunnel oven, packages of differently sized articles.
Furthermore, the provision of control systems for controlling the temperature of the air flow and for cleaning the article conveying chains, provides packages devoid of surface defects.